1. Field of the Invention
The present invention relates to an apparatus and method to transmit voice and other multimedia information over a network. In particular, an apparatus and method are provided which configure real time transport control protocol packets in a control feedback handling in multimedia sessions.
2. Description of the Related Art
Multimedia data is distributed by, for example, multimedia protocols. Real-time transport protocol (RTP) uses universal datagram protocol (UDP) as a transport protocol appropriate for transmission of streaming data; because UDP provides a fast transmission although not reliable like it is the case by transmission control protocol (TCP). Hypertext transport protocol (HTTP) and real-time streaming protocol (RTSP) run over the reliable TCP. The RTSP provides session control for streaming sessions. HTTP can be used for transmission of still images, bitmap graphics and text.
The RTP can provide end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. The functions provided by RTP include payload type identification, sequence numbering, timestamping, and delivery monitoring. The RTP contains a related RTP Control Protocol (RTCP) augmenting the data transport, which is used to monitor a quality of service (QoS) and to convey information about the participants in an ongoing session. Each media stream in a conference is transmitted as a separate RTP session with a separate RTCP stream.
RTP adds a time stamp and a sequence number to each UDP packet in a special RTP header. The time stamp is related to the sampling or the presentation or composition time of the media carried in the payload of the RTP packet. It is used for playing back media at the correct speed, and together with RTCP, it can be used for synchronizing the presentation of other streaming media. A payload specification defines the interpretation of the time stamp and other RTP fields. The recipient can use the sequence number to detect the loss of packets statistics on loss can be reported to the server by means of RTCP.
RTCP reports are capable of providing statistics about the data received from a particular source, such as the number of packets lost since the previous report, the cumulative number of packets lost, the interarrival jitter, etc. The RTCP control protocol is based on the periodic transmission of control packets to all participants in the session, using the same distribution mechanism as the data packets. The underlying protocol provides multiplexing of the data and control packets, for example using separate port numbers with UDP.
An apparatus and method are needed in which an excessive length of compound RTCP packets may be handled by fragmenting each compound RTCP packet in smaller non-compound packets and sending it spaced over time. The apparatus and method would guarantee RTCP non-compound packets to provide an equivalent functionality as the RTCP compound packets by providing the same information to the receiver (SR, RR, SDES, etc.), and the receiver would not lack any feedback information.